Immunomodulating properties of lymphocytes activated by farmer's lung associated bacterium Thermoactinomyces vulgaris in vitro.

Thermoactinomyces vulgaris, one of the aetiological agents of farmer's lung, was analysed for its ability to activate non-immune spleen lymphocytes from 10- to 14- week-old mice. The lymphocytes were found to exert both enhancing and suppressing signals after activation, depending on the secondary stimulation used. The enhancing effect is due to interleukin-2 secreted mainly by L3T4+ lymphocytes. The suppressive action is associated with Lyt2+ lymphocytes, which are probably activated by prostaglandins or histamine; but the suppression inducer action of L3T4+ lymphocytes may also be important. Genetic regulation, independent of H-2K and D, was also detected between different inbred strains of mice in response to T. vulgaris. The genetic regulation appeared associated with the different responsiveness of Lyt-2 positive lymphocytes between different strains. These results emphasize the importance of nonspecific activation in hypersensitivity disorders induced by microbiol antigens.